JPH039579B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an in-line color cathode ray tube electron gun, and in particular, the prefocus lens electrode thereof has a novel structure to reduce deflection distortion of the electron beam. , relates to an electron gun with improved focus uniformity across the entire display screen.

[Conventional technology]

Recent color display tubes are required to display high-density display, and color cathode ray tubes for displays are rectangular with sharp corners, and faces are becoming even more flat. Therefore, it is necessary to improve the electron beam focusing performance at the corners of the display screen more than ever before.

To explain the outline of the internal structure of an inline color cathode ray tube, as shown in FIG. There is. Three electron beams 6R, 6G, and 6B are emitted from the in-line electron gun 4 toward the screen 2 coated with red, green, and blue fluorescent substances. Further, a deflection yoke 5 for deflecting the three electron beams is provided in the neck glass section.

By the way, the magnetic field of the deflection yoke 5 that deflects the three in-line electron beams self-concentrates the two side beams 6R and 6B in the in-line array on the screen, so the horizontal deflection magnetic field is asymmetrical in the form of a pink tension. The vertical deflection magnetic field has a barrel-shaped asymmetric magnetic field distribution. Therefore, as shown in FIG. 4, when the electron beam 6 is deflected, the shape of the electron beam spot formed on the screen 2 is significantly deflected and distorted compared to the uniform magnetic field.
The shape of the beam spot becomes distorted and the focus performance at the periphery of the screen deteriorates.

As shown in FIG. 4, the side beams 6R and 6B in an inline arrangement and the center beam 6G receive deflection distortion differently, and the side beams 6R and 6B receive deflection distortion differently.
The deformation distortion of the beam spot 7 at the corner portion of the lens 6B is significant, and over-focused astigmatism (referred to as a halo) occurs around the beam spot 7, further deteriorating the focus quality. On the other hand, since the center beam 6G runs in the center of the deflection magnetic field distribution, it receives less deflection distortion, and the side beams 6R, 6
Compared to B, the beam spot 9 at the corner has a better shape and the halo is smaller.

Conventionally, in order to reduce distortion of the electron beam due to such a deflection magnetic field, improvements have been made to reduce the thickness of the electron beam 6 within the deflection magnetic field on the electron gun side. FIG. 5 shows a schematic cross-sectional view of a single electron gun among the conventional three-line inline electron guns. FIG. 5 shows a bipotential electron gun, in which an electron beam 6 is emitted from a cathode 45 that emits an electron beam, and the first grid 41 and second grid 42 control the amount of the electron beam and control the electron beam. 6 is accelerated, and the electron beam 6 is focused narrowly by the main electron lens _L1 consisting of the third grid 43 and the fourth grid 44, and the electron beam 6 is focused on the screen 2.
reach. By the way, in order to reduce the deflection distortion of the electron beam, it is necessary to make the divergence angle θ of the electron beam 6 incident on the main electron lens L ₁ as small as possible without making the electron beam diameter on the screen too large. There is.

For this reason, the second grid 42 and the third grid 4
Pre-focus lens formed in the part facing 3
Setting L ₂ to an optimal condition has been carried out.
Specifically, the second grid 42 and the third grid 4
3 and the plate thickness T of the electron beam passage hole 12 of the second grid 42, which will be described later, are set to optimal values. For example, a specific example is presented in Japanese Patent Application Laid-open No. 145472/1983. Figure 6a shows the second grid 42 used in the in-line electron gun 4.
This figure shows the shape of the x-y plane. There are three electron beam passing holes 12 arranged in line at equal intervals in the x-axis direction corresponding to the H-axis direction of the screen 2, and a reinforcing ring 13 for reinforcing the shape of each electrode is provided around each hole. .

The y-axis sectional view in FIG. 6b shows the electron beam passage hole 12.
The relationship between the diameter dφ of the electron beam passage hole and the plate thickness T at that part is the shape of the main electron lens.
It has been determined experimentally in relation to L ₁ . For example, when the main electron lens _L1 is of bipotential type, good results can be obtained by setting T=(0.4 to 1.0)d.

[Problem that the invention seeks to solve]

As described above, in order to improve the focus performance around the screen, it is possible to increase the hole plate thickness T of the second grid 42 and to optimize the electrode spacing between the second grid 42 and the third grid 43. However, when the electron beam is focused on the screen 2, the shape of the electron beam spot around the screen is improved in the vertical direction, but it has the disadvantage that it becomes too thick in the horizontal direction.

In other words, if the prefocus lens _L2 is made stronger, the beam divergence angle θ becomes smaller and the halo that occurs around the beam spot around the screen can be removed, but conversely, the prefocus lens
As L ₂ became stronger, the diameter of the virtual object point when viewed from the main lens L ₁ became larger, which tended to increase the diameter of the beam spot focused on the screen.

Therefore, in the present invention, the divergence angle θ of the electron beam 6 incident on the main lens _L1 is made different in the vertical and horizontal directions, and eight in-line electron beams 6 are used.
The present invention proposes a prefocus lens L ₂ that has an optimal vertical divergence angle θy and can optimally focus the three in-line electron beams 6 over the entire screen.

[Means for solving problems]

In this invention, around the grid electrode constituting the prefocus lens, that is, the center beam 6G and side beams 6R, 6B passage hole 12 provided in the second grid 42, on the prefocus lens side. Recesses 14 and 15 having a long shape in the inline arrangement direction are provided, and the widths D ₁ and D ₂ of the recesses 14 and 15 in the direction perpendicular to the inline arrangement direction are such that the width D ₁ of the recesses with respect to the center beam 6G is the side It is made to be larger than the width D ₂ of the recess for the beams 6R and 6B.

[Effect]

The operation of the above configuration will be described according to the electron optical model diagram in FIG. 3. The electron beam 6 emitted from the cathode 45 is prefocused by the prefocus lens _L2 of the present invention, Due to the presence of the elongated recesses in the inline arrangement direction, the divergence angle of the electron beam differs between the horizontal direction (x-axis) and the vertical direction (y-axis). That is,
θx>θy. Therefore, the electron beams 61 and 62 heading toward the main lens _L1 receive different refractive powers on the main lens _L1 surface, and the convergence angle toward the screen 2 is smaller in the vertical direction than in the horizontal direction, which reduces deflection magnetic field distortion. At the periphery of the screen 2, the electron beam receives the convergence force of the deflection magnetic field in the horizontal direction, and the electron beam is focused in the vertical direction without being over-focused. As described above in FIG. 4, each electron beam 6
Since the deflection magnetic field distortions that G, 6R, and 6B receive from the deflection magnetic field are different, by making the width D ₁ of the recess for the center beam 6G larger than the width D ₂ of the recess for the side beams 6R and 6B, the center beam By varying the relationship of θx - θy between 6G and side beams 6R and 6B while maintaining the state of θx > θy, optimal correction of each in-line type electron beam for deflection magnetic field distortion can be performed, and corner portions can be corrected optimally. Focus performance can be improved.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

Figure 1 shows the pre-focus lens of this invention.
This shows the second grid 42 that constitutes _L2 .
A is a front view, b is an enlarged x-axis sectional view, and c is an enlarged y-axis sectional view. Similar to the conventional second grid 42, there are three electron beam passing holes 12 at equal intervals in the x-axis inline direction.
Rectangular recesses 14 and 15 long in the x-axis direction are provided around the prefocus lens side. As shown in the enlarged x-axis sectional view of FIG. 1b and the y-axis enlarged sectional view of FIG.
The shapes of the recesses 14, 15 facing the grid 43 are different. That is, in the horizontal deflection direction, the recess length E is increased to strengthen the convergence force of the electron beam, and in the vertical deflection direction, the recess widths D ₁ and D ₂ are changed to the above-mentioned recess in order to reduce the beam divergence angle. It is narrower than the length E. For example, dφ=0.4mmφ
In the case of D ₂ = 0.5mm, E≧3D ₂ , A = 0.1~0.15mm
It is better to make it .

By the way, since the center beam and the side beams receive deflection distortion differently, it is necessary to make the width D ₁ of the recess 15 for the center beam different from the width D ₂ of the recess 14 for the side beam.
That is, it is important to maintain the relationship D ₁ >D ₂ . The value of (D ₁ −D ₂ ) must be selected depending on the deflection yoke method and main lens method. for example,
When dφ=0.4mmφ, good results can be obtained by setting D ₁ −D ₂ =0.1 to 0.2mm.

〔Effect of the invention〕

As described above, by providing a long recess in the x-axis direction around the hole of the second grid that constitutes the pre-focus lens, convergence performance in the horizontal direction is improved and deflection distortion is reduced in the vertical direction. I am now able to correct it. Furthermore, by making the width of the recess different for the center beam and the side beam, and making the width of the recess larger for the center beam, it has become possible to perform optimal deflection distortion correction for each in-line electron beam. Therefore, by employing the second grid of the present invention, it is possible to improve the screen uniformity of the focus for an in-line type color cathode ray tube for a display, and it is possible to improve the resolution in the horizontal direction more than before.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the second grid electrode used in the electron gun according to the present invention, in which a is a front view, b is an enlarged sectional view on the x-axis, and c is an enlarged sectional view on the y-axis. is a side view schematically showing a general in-line color cathode ray tube, Figure 3 is an explanatory diagram showing the basic electron optical system, and Figure 4 is a diagram showing the beam spot shape around the screen in a conventional in-line color cathode ray tube. , a is an explanatory diagram of the side beam, b is an explanatory diagram of the center beam, FIG. 5 is a schematic cross-sectional view of a conventional bipotential electron gun, and FIG. 6 is a diagram of the second grid of a conventional in-line electron gun. 2, in which a is a front view and b is an enlarged y-axis sectional view. 1... In-line color cathode ray tube, 4... Electron gun, 6... Electron beam, 6B, 6G... Side beam, 6R... Center beam, 12... Passing hole, 14, 15... Recess, 42... ...Second grid electrode, D...Concave line, E...Concave length, L ₂ ...
pre-focus lens. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. In an in-line color cathode ray tube electron gun, an in-line arrangement direction is provided around the pre-focus lens side of the center beam and side beam passage holes provided in the grid electrode constituting the pre-focus lens. A long-shaped recess is provided in the recess, and the width of this recess in the direction perpendicular to the inline arrangement direction is such that the width of the recess around the center beam passage hole is larger than the width of the recess around the side beam passage hole. Characteristic electron gun. 2. The electron gun according to claim 1, wherein the shape of the recess is rectangular.